Broadcast 1 November 1990, this programme explores forms of navigation. Attenborough starts in Africa at dusk, by describing some of the species that don t rely on sight. The spotted hyena uses its acute sense of smell to guide it while it hunts nocturnally, while galagos urinate on their hands so they can completely mark their movements. Some animals use echolocation and these include swiftlets, bats and river dolphins.